1. Field of the Invention
The invention relates to a fluid power transmitting device provided in a vehicle.
2. Description of Related Art
A vehicular fluid power transmitting device provided in a power transmission path between a power source of a vehicle and an automatic transmission is known. This vehicular fluid power transmitting device transmits torque generated by the power source to an input shaft of the automatic transmission via fluid. Some known examples of a vehicular fluid power transmitting device are a fluid coupling and a torque converter. A fluid coupling is provided with a pump impeller and a turbine runner. The pump impeller is rotatably driven about an axis by a drive source such as an engine. The turbine runner is rotated about this axis by operating fluid that is pushed out by the pump impeller. A torque converter is described in Japanese Utility Model Application Publication No. 05-050202 (JP 05-050202 U), for example. The torque converter is also provided with a stator that is arranged between the pump impeller and the turbine runner, in a manner rotatable about the axis.
In such a vehicular fluid power transmitting device as that described above, an input device such as a drive plate or a damper device inputs torque from an engine that is the drive source of the vehicle to the pump impeller. The input device is provided with protrusions that are attached in a protruding manner in a plurality of locations at predetermined intervals on the circumference of a circle to a pump shell of the pump impeller by welding or the like. The input device is fixed to the pump shell by a plurality of nuts or the like that screw onto the protrusions. Alternatively, the input device is fixed to the pump shell by a plurality of set bolts that screw into a plurality of set blocks. Here, the plurality of set blocks are fixed at predetermined intervals on the circumference of a circle by welding or the like to the pump shell of the pump impeller.
In the fluid power transmitting device described in JP 05-050202 U, a damper device is provided between a crankshaft of the engine and the set blocks that are fixed to radially outer portions of the pump shell. Therefore, springs of the damper device are positioned farther to the radially inner side than the set blocks, so damper performance is unable to be sufficiently obtained. In contrast, it is conceivable to move the set blocks to the radially inner side of the pump shell, and position the springs of the damper device that are provided between these set blocks and the crankshaft of the engine on the radially outer side of the set blocks.
With this structure, a front side of the pump shell is formed curved so as to form a relatively large space between the pump shell and the drive plate that is fixed to the shaft end of the crankshaft, and interpose the damper device therein. Therefore, when the pressure of operating oil inside of the pump shell increases or centrifugal force is applied when the pump shell rotates, in particular, the amount of deformation toward the rear where the radially inner side on the front side of the pump shell becomes the fulcrum increases. Therefore, the plate thickness of the pump shell must be increased to inhibit this expansion and deformation amount, which decreases formability and increases manufacturing cost, which is problematic.